Clinical and Laboratory Studies are conducted to determine etiology (infection, immunity and/or genetics) for chronic diseases of the central nervous system. Current studies include Multiple Sclerosis, Progressive Multifocal Leukoencephalopathy, Subacute Sclerosing Panencephalitis, Amyotrophic Lateral Sclerosis and Parkinson's Disease. Combined clinical data, genetic information, HLA and MLC typing, virus serology and virus isolation studies are obtained in these investigations. New prophylactic and therapeutic materials are studied for the prevention and control of these diseases in volunteers and patients. Current studies include evaluation of rubeola vaccines for immunogenicity in relation to SSPE and cellular and humoral immunity in individuals with Progressive Multifocal Leukoencephalopathy. BIBLIOGRAPHIC REFERENCES: Johnson, T., Knobeloch, L., Sunderland, E., Juhl, U., Steinhart, C., Scott, G., Varakis, J., Fuccillo, D., Sever, J.L. and Kornguth, S.: Crystals, Paracrystals, and Rigid Tubules in Multiple Sclerotic Brain and Spinal Fluid. Lab. Invest. 35: 264, 1976. Fuccillo, D., Kurent, J.E., Manne, S.H., Rosenthal, D., Beadle, E., and Sever, J.L.: Lack of Association Between Defective Delinquents and Antibody of Herpesvirus Hominis. Neurol. 27: 304-305, 1977.